diff --git a/compact.go b/compact.go
index 211c5e9..280cbd4 100644
--- a/compact.go
+++ b/compact.go
@@ -41,6 +41,13 @@ func (compactOptions CompactOptions) Normalised() CompactOptions {
 
 // Usage example: `if err := (store.CompactOptions{Before: time.Date(2026, 3, 30, 0, 0, 0, 0, time.UTC), Format: "gzip"}).Validate(); err != nil { return }`
 func (compactOptions CompactOptions) Validate() error {
+	if compactOptions.Before.IsZero() {
+		return core.E(
+			"store.CompactOptions.Validate",
+			"before cutoff time is empty; use a value like time.Now().Add(-24 * time.Hour)",
+			nil,
+		)
+	}
 	switch lowerText(core.Trim(compactOptions.Format)) {
 	case "", "gzip", "zstd":
 		return nil
diff --git a/compact_test.go b/compact_test.go
index f1e2cf2..350449a 100644
--- a/compact_test.go
+++ b/compact_test.go
@@ -201,6 +201,14 @@ func TestCompact_CompactOptions_Good_Validate(t *testing.T) {
 	require.NoError(t, err)
 }
 
+func TestCompact_CompactOptions_Bad_ValidateMissingCutoff(t *testing.T) {
+	err := (CompactOptions{
+		Format: "gzip",
+	}).Validate()
+	require.Error(t, err)
+	assert.Contains(t, err.Error(), "before cutoff time is empty")
+}
+
 func TestCompact_CompactOptions_Good_ValidateNormalisesFormatCase(t *testing.T) {
 	err := (CompactOptions{
 		Before: time.Now().Add(-24 * time.Hour),